Hydromechanical automatic progressive power ratio transmission system



INVENTOR El? ,5"0 in 2 Sheets-Sheet l ATTORNEYs P. E. SJODIN N bhmh.

POWER RATIO TRANSMISSION SYSTEM HYDROMCHANICAL AUTOMATIC PROGRESSIVE MarchA 15, Filed Jan. 50, 1956 P. E. SJODIN HYDROMECHANICAL AUTOMATIC PROGRESSIVE March 15, 1960 POWER RATIO TRANSMISSION SYSTEM 2 Sheets-Sheet 2 Filed Jan. 30, 1956 'i' INVENTOR R'. Sja d z' n,

n wll M NN ATTORNEYS United States Patent() HYDROMECHAICAL vAUTOMATIC PROGRES- SIVE'POWER RATIO TRANSMISSION SYSTEMl l 4Peter E. Sjodin, San Antonio, Tex. Application January 30, 1956, Serial No. 562,176

3 Claims. (Cl. 60-54.6)

The present invention relates to hydraulic systems, and more particularly, to such systems that include means to intensify the pressures exerted on the hydraulicuid to multiply the forces exerted thereby.

The primary object of the invention is to multiply the'forces exerted by the brake pedal on the hydraulic brake iluid to create the effect of power brakes without increasing the stroke of the brake pedal.

Another-object of the invention is to provide a hydraulic system having a pressure intensifying action which occurs after the initial slack has been removed Yfrom the system.

A further object of the invention is to 'provide a hydraulic system incorporating means for intensifying the pressure exerted on the hydraulic iluid which Ais operated completely by the action of' a single lever with the,

intensifying action occurring at a predetermined pressure of the hydraulic iluid. f 'p i 'A still further object of the inventionV is'to provide a structure of the class described whichwill be inexpensivev to manufacture, simple to installand adjust, and relatively free from' maintenance problems `throughout the elective life thereof. p

Otherobjects andv advantages will become apparent in the following specification when considered in the light of the attached drawings, in which: v

Figure l is a longitudinal section taken through the medial line of the master cylinder of the invention'. Figure 1A is a continuation of Figure 1 illustrating the pressure control unit. 'f

Figure 1B is a continuation ofY Figurel illustrating the secondary intensify-ing unit.

Figure 2 is a side elevation of the cylinder of the control mechanism. k

Figure 3 is a transverse cross-section taken along the line l3 3 of Figure 1A, looking in the directionof the arrows. l

Figure 4 is a transverse` fragmentaryl cross-section taken along the line 4-4 of Figure 1, rlooking in the direction of thearrows. f

Figure 5 is an end elevation of the torsion spring mounting plate.

Figure 6 is a fragmentary longitudinal cross-section taken along the line -fof'Figure 1A, looking' in the direction of the-arrows. r Figure 7 is a side elevation 'of the master cylinder piston. A A y Referring now to the drawings in detail whereinlike reference numerals indicate likelapart's' throughout.Y the several figures, the reference numeral'fllindicates `generally a master cylinder having a reservoirk .11 closed by a filler cap 12 having a vent v13 extending therethrough to the atmosphere. A cylinder 14 extends across the bottomof the master cylinder and is provided'wit a port15 communica-ting with ,the reservoir 11. i-

- A `cylinder 16 extends Yaxially of the cylinderf14and Y cylinder 16 is internally threaded at its outer end at 17.V The cylinder 14 is provided with an annular groove 181 adjacent theA end thereof opposite the cylinder 16. An end wall 19 is positioned within the cylinder 14 and supf` ported therein by spring ring 20 engaged in the groove 18. A linkv21 projects through the center of the end wall 19 and engages a master cylinder pistou, generally indicated at 22. The master cylinder piston 22 is provided with a cylindrical portion 23 having a recess 24 extending into one end thereof and adapted to receive the link 21. An elongated cylindrical body 25 extends from the cylindrical portion 23 and is provided with a longitudinally extending slot 26 extending completely therethrough. A second cylindrical portion 27 of the same diameter as the cylindrical portion 23 is integrally formed on ,thepiston 22 at the end thereof opposite the cylindrical portion 23. The cylindrical portion 27 is provided with an axial threaded bore 28 which communicates with the slot 26 at one end and the end of the cylindrical portion 27 at the other end. f

An annular groove 29 is formed in the cylindrical body 25 adjacent the cylindrical portion 23. A rubber piston cup 30 having a diameter to engage the side walls of the cylinder 14 is positioned so that the rear portion thereof engages within the annular groove 29. A second piston cup 31 is positioned within the cylinder 14 in engagement with the end face of the cylindrical portion 27. A coil spring 31A has one end engaging the rubber cup 31, and the other end engaging the endof the cylinder 14.

A cylinder 32 is provided with external threads 33 adjacent one end thereof which cooperate with the threads'28 of the cylindrical portion 27 to hold the cylinder 32 therein. A reduced tubular extension 34 projects from the cylinder 32 and carries a piston 35 adjacent n the outer end thereof with the piston 35 extending into threadedly attached and is positioned across the cylinder ingrtvhrough the slot 26 into the side walls of the cylnder 14. A head 43 is attached to the pin 42 and threads into the cylinder 14 to support the pin 42 therein. The

valve 40 is adapted to engage and close the port 37 in the wall 36.

A valve'piston 44somewhat smaller in diameter than the piston 40 is' mounted for reciprocation in the cylinder 32 between the wall v38 andthe end of the cylinder 32. The valve 44-is provided with a piston pin 45 which extends through the bore39 in the. wall 38 to engage the valve 40. However, thisengagernent of the piston pin'45l and the valve 40 will not occur when the valves 40 and 44 are. in closed position. V.Both the piston 40 and the piston 44 are provided with ports 46 and 47, respectively, to permit the passage of fluid therethrough. A stop 48 is formed on the outer side of the piston 44 to engage` against the end of the cylinder 32 thus limiting v the movement of the piston 44.

projects outwardly from the master. cylinder 10. The l,

A pluralityof ports 49 extend through' the stop 48 to permit the ow of tluid from the cylinder 32 to the tube 34 or from the tube 34 to the cylinder 32 when the piston.44 is in its fully extended position. The cylinder 32is.provided with a plurality of ports 50 to permitvthe Patented Mar. is, vwaol freie" of fluid between the cylinder 14 and the ,cylinspring 52 engages the end of the cylinder 3'2` at one end i and the piston 44 `atthe other and biases the piston 44 into position to close the port 39 under normal conditions.

The tubular extension 34 is provided with a bore 53 which extends completely through the piston '35. A ange 54 projects beyond the piston 35 and forms a guide for a rubber piston cup 55 which is adapted to reciprocate in the cylinder 16. v

A fitting 56 having an externally screw threaded extension 57 and a bore 57A is mounted in the end of the cylinder 16 by means of a thread 17. The fitting 56 has a fiange 56A which engages a' gasket 56B to seal the fitting 56 against the end of the cylinder 16. A valve seat 58 is positioned against the inner end of the threaded extension 57. A disk valve 59 engages against the Valve seat 58 closing the bore 57A of the fitting 56. A coil spring 60 engages the valve 59 at onerend and the cup 55 at the other, normally biasing these members against their supports.

A valve 61 having a valve stem 62 extending therefrom projects through a bore 63 in the valve 59. A head 64 is formed on the end of the valve stem 62 and a spring 65 extends between the head 64 and the valve 59 normally maintaining the valve 61 in bore 63 in closing position. An adjustable fitting 66 is secured to the outer end of the fitting 56 by means of a hollow bolt v67A.

, A conduit 68 extends from the cylinder j 14 and a second conduit 69 extends from the reservoir 11. A conduitv70 extends from a fitting 71 on the fitting 66 and an elbow 72 extends from the tting 66 to a coupling 73.

A body 74, illustrated in Figure lA, is positioned adjacent the master cylinder 10 and adapted to be connected thereto by conduits 68 and 69 and elbow 72. The body 74 is provided with a bore 75 closed by an end wall 76 having a threaded bore 77 extending therethrough. A fitting 78 ris threadedly connected to the threaded bore 77 at yone end and to the conduit 68 at the other end. Arbleeder fitting 79 extends through the side of the bore 75 for purposes to be described. A bore V80 extends axially of the body 74 and is connected to the bore 75 by-means of a port 81.

A threaded bore 82 extends radially from the bore 80 at the end thereof adjacent the port 81. A' fitting 83 is threadedly connected to the threaded bore 82 at one end andV to the conduit 69 at the other end. An axial bore 84 having a diameter somewhat larger than the bore communicates with the ybore 80 and extends through the end 85 of the body 74. The bore 84 is internally screw threaded at S6 for purposes to be described.

A cylinder- 87 is provided with an internal' bore 88 which is threaded at 89 adjacent one end of the cylinder 87. The cylinder 87 is provided with a bleederfitting 90 in communication with the bore 88. A longitudinal slot 91 extends inofthe cylinder 87 from the end thereof opposite the threads 89 and communicates with thek bore 88. The end ofthe cylinder S7 containing the longitudinal slot 91 is externally threaded at 92 and is' adapte-d to be threadedly engaged in the bore 84 as' illustrated in Figure 1A.

A lock nut 93 engages the threads 92 on the cylinder 87 and the end 85 of the body 74 to lock thev cylinder 87 to the body 74. A piston94 is mounted for reciprocation in the cylinder 88 and is providedv with a pair of oppositely extending ears 95 and 96 projecting through the slot 91 in the cylinder 87. The piston 94 is provided with a piston rod 97 which extends through the bore 84, the boreSO, the port 81, and into the bore 75.A The outer end 98 of the piston rod 97 is externally threaded 42S and .carries a piston??audrubberpiston CHP 1.00 thmon clamped between clamping nuts 101 and 102.

A valve 103 is secured to the piston rod 97 by means of clamping nuts 104 and 105. The valve 103 is positioned within the bore 75 and is adapted to engage the port 81 to prevent communication between the bore 75 and the bore 80. The piston99` and the piston cup 100 are positioned withinl the bore and are adapted to prevent` communication between the bore 80 and the bore 84.

A torsion springJK mounting plate 106 is positioned within the bore 88 and has a pair of ears 107 and 108 projecting outwardly therefrom through the slot 91` in the cylinder 87. A pair of locking stop nuts 109 and 110 engage over the threads 92 on the cylinder 87 and provide a positive stop for the torsion spring mounting plate 106. Another pair of locking clamp nuts 111 and 112" lare likewise engaged over the threads 92 of the cylinder 87 to form a stop for the` piston 94.

lA torsion coil spring 113 is positioned over the piston rod 97 in engagement with the piston94 at one end and the `torsion spring mounting plate 106 at the other end. A rubber piston cup 114 isl positioned `against the piston 94 to sealthe bore 88. A fitting 115 is threaded into the threads 89 at thevend of thepbore 88 at one end thereof and has a radial liange 116 extending outwardly therefrom to engage a gasket 117 lying against the end of the cylinder 8 7. v

A coupling 118 is detachably secured to the fitting 115 and supportsV a conduit 119 in communication with a port 120 extending` through the fitting 115. A coil spring 121 engages against the inner end of the fitting 115.at one end and the piston cup k114 at the other end. The conduit 119is connected to the coupling 73 to communicate with the elbow 72.

Referring now,V to Figure 71B, a body 122 is provided with a bore 123'Vhaving an internally threaded end portion 124. A reduced portion. 125 extends axially of the body 122 and has a bore 1,26 therein extending axially of the bore 123 and in communication therewith. `The end` of the bore 126 opposite .the bore 123 is internally threaded as at 127. VA fitting 1281S threaded into vthc threads 127 and hasl an annular flange 129 extending outwardly therefrom in engagement with gasket 130 positioned against the end of the reduced portion 125.

A conduit 131 Vis secured to thegitting 128 by a coupling 132 and communicates with the bore 126 by a port 133 extendinglthrougjh the fitting 128.` The conduit 131 extends to a pressure responsive device (not Shown).-

A cover plug 134 provided with a flange 135 anda screw. threaded portion 136 which is adapted to be threaded into the threads 124 of the bore 123 with the ange engaging against a gasket 137 effectively closes the bore 123. A piston 138 is mounted for reciprocation in the bore 126 and has a' rubber piston cup 139 positioned thereagainst. A coil spring. 140 engages against the piston cup 139 at one end and the fitting 128 at the other end normally biasing the piston cup 139 against the piston'138. l

A bleed'er fitting 141V issmounted in communication with the bore 126 for purposes to be explained( The piston 138 .is provided with an elongated piston rod 142 extending through the bo-re 123 and having a threaded end portion 143. A piston 144 is mounted over the piston rod 142 within the bore 123 and has a piston cup 145 engaged thereagainst.

A pair of clamping nuts 146 andV 147 secure the piston 144 and piston cup 145 and a washer 148 in clamped relation on the piston rodi-142. An adjustable stop nut 149 is threadedv onto' the end of the piston rod 142and clamped in adjusted position thereonby the lock nut 150. A'blee'der fitting 141A is mounted inI communication with the bore 123 for purposes to be explained;

A threaded bore 151 extends through the side of the body 122 incommunication with the bore 123 adjacent the cover plug '134. A 'fitting 152 is threaded into the threaded bore 151 and has an internally threaded bore 153 extending from the inner end thereof. An annular shoulder 154 projects into the bore 153. A threaded bore 155 `projects into the fitting 152 from the opposite end to the threaded bore 153 and extends into the shoulder 154.' A fitting v156 is threadedly engaged in the threaded bore 155 and has a flange 157 thereon clamping a gasket 158 against the end of the fitting 152.

A coupling 159 secures a conduit 160 to the fitting 156 in communication with a port 161 extending throughV the fitting 156. The conduit 160 is connected to a condut`70 extending from themaster cylinder 10.

An adjustable plug 162 is threadedly engaged in the threaded bore 153 and has a port 163 extending therethrough. A valve 164 engages the shoulder 154 to close the bore 155. A coil spring 165 engages the valve 164 at one end and the plug 162 at the other end normally biasing the valve 164 against the shoulder 154.

A port 166 extends through the valve 164 and is closed by a valve 167 having valve stern 168 extending therethrough. A head 169 is formedk at the free end of the valve stem 168 and engages a coil spring 170 which extends therefrom to the valve 164 normally biasing the valve 167 into port 166 closing position.

The offset portion 125 of the body 122 is provided vwith a downwardly offset portion 171 havinga bore 172 extending through 'one end thereof. The bore 172 is threaded at 173 adjacent the outer end thereof. A bore 174 extends axially of the bore 172 in communication therewith and is somewhat smaller in diameter than the bore 172. The bore 4174 is communicated to the atmosphere by means of a port 175. A port 176 connects `the bore 126 with the bore 172.

A fitting 177 is connected to a port 178 in communication with the bore 174 and has a conduit 179 secured thereto by means of a coupling 180. The conduit 179 is connected at the other end thereof to the conduit 70. A; tting 181 is threaded into the threads 173 of the bore 172 and has a flange 182 whichengages against a gasket 183 to seal the fitting 181 against the end of the oiset portion 171. Y j

A coupling 184 secures the terminal end of the'conduit 70 to the fitting 181 in communication with the port' 185 extending therethrough. The tting 181 has an internally 'threaded shallow bore'186 extending axially from the 'inner end thereof. YA plug 187 is threaded into the bore 186 andis provided with avhore 188 extending axially therein from the threaded end. A bore 189 communicates the bore 188 through the opposite end of the plug 187.

iA port 190 extends through the side wall of the bore `188. A bypass valve 191 is mounted within the bore 188 and is adapted to engage against the fitting 181l to close the port 185. A valve stem 192 extends through the bore 189 to support the valve Y191 and has a coil spring 193 engaged thereover extending between the valve 191 and the inner end of the bore 188. The coil spring`193 normally 4biases the valve 191 into port 185 closing position.

A coil spring 194 is positioned within the bore 123 betweenthe piston 144 .and an end of the bore 123 so as to normally bias the piston 144 toward the cover 134. A vlink 195 is engaged against the end ofthe pistonA 138 havingV the pistonV rod 142 extending therefrom and projects outwardly through a port 196 in the reduced portion 125. '-A- pivot 197 pivotally secures the link 195 to a yoke 198 mounted on the cylinder 122i` YAn adjustable stop ,199 vis threadedly attached to the outer end of the link 195 and locked thereon by means of a lock nut 199A. k v l A piston 200 is mounted on a piston'rod 201 and is adapted t reciprocate in the bore 174.` The piston rod 201l extendsl through the port 175 and engages against the stop 199. The pistonrod 201 is providedfwith an annularshoulder 201A in spaced apart relation tothe piston 200. A rubber piston cup 202 of a diameter to engage vthe inner wall of the bore 174 is positioned between the piston 200 and the annular shoulder 201A. A valve 203 is secured to the inner end of the piston rod 201 to engage the end of the bore 174 sealing it from the bore 172. yThe piston 200 and the piston cup 202 are positioned within the bore 174 to prevent communication between the uid in the bore 174 and the atmospherefl The valve 191 isadapted to be used as a bypass valve only, and remains closed during all normal operations in lmost hydraulic systems, being used only when the uid pressure in the. conduit 70 exceeds the uid pressure' in the conduit 131. This would be true in hydraulic systems such as pressure molding, die-forming, and/or punch press machines after steps of operation are cornpleted and slack lin the system develops between steps.

In the use and operation of the invention, the hydraulic system is filled with fluid in the conventional manner through the master cylinder ller port, closed by the filler cap12. The air is bled out of the system in the Y conventional manner through the bleeder valves 79, 90,

141, 141A and all other bleeder valves in the system (not shown). The external operating force (not shown) v in engagement with the link 21 moves the piston 22 to the right, as viewed in Figure 1, causing the cylindrical portion 27 to exert pressure on the fluid in they cylinder 14. y l

The fluid pressure in the cylinder 14 and the spring 51 moves the piston valve 40A to the left to close the port 37 in the wall 36 as the valve stem 41 leaves the-trip bar '42, and the fluid ows from the cylinder 14 through the ports into the cylinder32, moving the valve 44 against the end wall of the cylinder 32. The fluid will ow through the bore 39, port 47, port 49, bore 53, cylinder 16, opening the valve 61 and through the bore v63 in the valve 59 and then through port 57A and into the conduit 70. The fluid will flow from the conduit 70A through theconduit 179, port 178 into the bore 174, around the valve 203 into the bore 172, -as viewed in Figure 1B, through the port 176 into the bore 126, through the port 1.33, through the conduit 131 into the final, pressure responsive device (not shown).

. After the initial slack has been removed from the systemand thepredetermined amount of pressure is reached .161. The valve 164 is forced oi its seat permitting the fluid to ow through the port 163 into the `bore 123 moving the piston 144 to the right, as viewed in Figure 1B, ,against` the torsion spring 194. Movement of the piston 1'44 causes the piston rod 142 to move the piston 138 to the right. As the piston 144 and the piston 138 move to the right, the link in, engagement with the rear of the piston 138 is permitted to rotate about the pivot 197 to release the .stop 199. The valve stem 201 in engagement with the stop 199 is released which permits the fluidunder pressure in the bore 174 bearing against the piston 200 to close the valve 203 in the bore 174.`

Further movement of the piston 138 in the bore: 126, as a result of continued exertion ofthe external force, will elect' a pressure in the conduit 131v above that which is inthe conduit 70, and hence will apply a'y greater amount of pressure for purposes to be assigned, than is normally possible.

When it is desired to adjust the relative pressures affecting the pressure intensifying piston 35, the spring vstop 106 is moved toward or away from the piston 94,

as the case may be, by'adjusting the stop nuts 109 and 110.\ The torsion of the spring 113 is thus varied to permit thepiston 94 to operate at differentpressures'. The pressures operating the piston 94 causes the valve 1113 toy open duey to the movement of the valve' stem 97 thus releasing the pressure in the cylinder 14. The release of pressure in the cylinder 14 will permit the spring 52 to move the valve 44 tothe left closing the port 39, converting the cylinder 16 into a' pressure producing cylinder with further movement of the piston 35 therein increasing the pressure on'the' fluid.

Also as the valve 103 is opened, the fluid is permitted to flow from the cylinder 14 upon the' forward motion of the cylindrical portion 27 through the conduit 68 into the bore 75 of the' body 74,7through` the port 81 into the bore 80, through the conduit 69 and into the reservoir 11, releasing all pressure from the cylinder 14' and keepingit released as long as the piston 35 is activated. All of the external operating force is thus transmitting pressure to the piston 35, the smaller area of which consequently intensifies the pressure in the conduit 70. l

The unit illustrated in Figure 1B receives the intensified pressure which is applied against the piston 144 and with the system being closed off Ybetween the conduit 70 and the conduit 131, the smaller piston 138 intensiyfies the pressure applied to the piston 144. Obviously,

the difference in cross-sectional areas between the cylindrical portion 27 and the piston 35, and the piston 144 and the piston 138 must be determinedv to obtain the final pressure multiplication involved.

As the pressure is released by the external operating force from the master cylinder piston 22, the spring 31A along with the spring 60 will begin to move the piston 22 back to the left, as viewed in Figure 1, releasing the pressure in the conduit 70.

The spring 113 will move the piston 94 to the right, as viewed in Figure 1A, closing the valvev 103 in the port 81.

The valve 167 in the port 166, as viewed in Figure 1B, opens as the fluid starts back toward the master cylinder 10.

As the master` cylinder piston 22 continues to move back to the left, as viewed in Figure l, the valves 40 and 44 will open. The atmospheric pressure from the vent 13 in the filler cap 12,on the Vfluid in the reservoir 11 counteracts the partial vacuum created infront of the cylindrical portion 27 and the piston 35 by the backward motion of the piston 22, moving the uid from the reservoir 11. This partial vacuum created will cause the atmospheric pressure to force the fluid from the master cylinder reservoir 11 through the port y15 into the cylinder 14 through the slot 2,6, port 37, port 46 and into the cylinder 3?. through the ports 50 and into the cylinder 14 and also 'through the port 39, port 47, port 49, bore 53 and into the cylinder 16, filling the cylinders 14 and 16 so it will be possible to pump more fluid into the conduit 70 if that is desired and if the master cylinder 22 is immediately urged forward again.

As the master cylinder piston 22 returns to the initial point as illustrated in Figure l, the piston rod 41 will engage the stop pin 42 holding the valve 4l] open away from the port 37. The piston pin 45 vin engagement with the valve 4u will hold the valve 44'open away from the bore 39'. i

As the excess fluid in the bore 123 returns to the conduit 70 through the port 166 of the valve 167 and Vthrough the conduit 164), as viewed in Figure 1B, the spring 194 along with the spring 140 will move the pistons 13S and 144 to the left releasing the pressure in the conduit 131. As the pistons 138 and 144 return to the initial point, as illustrated in Figure 1B, the piston 138 will engage the link 1%'. The link 19S will rotate about the pivot 197,

-and the stop 199 in engagement with the valve stem 201 V.will move the valve293 to the right opening the bore '174, The' excess fluid in ,the cbnsiuit 131, used there lto 8 'take up slackl in the system,--will return'toward the master cylinder 10 lowing throughl the port 133 into the bore 126 through the port 176 into'the bore 17,2 by the' valve 2931 into the bore 174 through` the porty 178,; conduit 179 and into the conduit 70.

As the excess fiuid in the' conduit 70 returnsl to the master cylinder 10 through the bore5s7A, the valve 59 will move off its seat 58,- as viewedl in Figure 1, and the fluid will flow around the valve 59 into the cylinder 16 through thhe boreV 53, port 49 and into the cylinder 32 through the port 47, port 39, port 46, port 37, slot 26 and into the cylinder 14 through the port' 15 and into the reservoir 11. Y As all the excess fluid in the system, used there to take up the slack, is returned to the reservoir 11, the valve 59 seated by the spring 60, as illustrated in Figurel, will retain a small amountr of fluid pressure in the complete forward system. The valve 167 seated by the spring 170, as illustrated in Figure 1B, will retain an additional small amount of uid pressure in the bore 123.

This amount of retained uidpressure is necessary to keep all the rubber cups in shape and sealed against their respective cylinder walls so no air will enter the system.

The unit illustrated in Figure 1B is set by means of the adjusting plug 16'2 and is set to operate to open the valve 164 when suficient pressure has been applied to the system to take up the lost motion.

The unit illustrated in Figure 1A is set by means of the stop nuts 109, and is set to operate to open the valve 163 when suf'licient pressure has been applied to the system to exceed by several pounds perl square inch that needed to put the unit illustrated in Figure 1B into operation.

Having thus described the preferred yembodiment of this invention, it should be understood that numerous modifications and structural adaptations may be resorted to without departing from the scope of the appended claims.

What is claimed is: y

1. A iluid pressure system comprising means including a piston for applying an initial low pressure to said systern, a high pressure means including a secondv piston rigidly secured to said first piston for intensifying the pressure in said system, means actuated by the initial pressure of fluid in said system for simultaneously deadtivating said low pressure means and activating said high pressure mean, a second means actuated by the `initial pressure of tiuid in said system for further deactivating said low pressure applying means and simultaneously activating a secondary highrpressure means for further intensifying the pressuresin saidV system and means for bypassing said first high pressure applying meansV with pressures from said secondary high pressure applying means upon failure of said first high pressure applying 1 means.

2. A fluid pressure attachment for hydraulic pressure systems comprising afmeans for successively exerting low and high pressures on the fluid in said system, means yresponsive to pressures in said system for adjusting said exerting means from low pressure to high pressure, a pressure intensifying cylinder having aY pair of axially .aligned bores of different diameters, a piston, mounted in each bore, meansconnecting said pistons for simultaneous reciprocation, means communicating the larger of said bores with said means for exerting low and high pressures Vfor actuation of 'said piston therein by fluid pressurefrom said exerting means, vmeans communicating the smaller bore with said exerting means, means communicating the smaller bore with a fluid pressure responsive means,- and means for closing the means communicating'the smaller bore with said exerting means whereby the pressures' exerted by said piston in said smaller bore will be extended solely tothe said fluid pressureresponsive means.y

3. A device as claimed in claim 2 wherein said means c mlling said pistons for simultaneous reciprocation rs Referencs Cited in the file of this patentA UNITED STATES PATENTS y Lepersonne Feb. 13, `1940 Hirsch Mar. 26,1940

10 l Swift Feb. 10, 1942 yPallady July 28, 1942 Fowler Apr. 27, 1943 Freeman Jun 8, 1943 Goepfrich June 20, 1944 Carter Sept. 13, 1955 Troy Mar. 27, 1956 Highland Ian. 21, 1958 

